<?php
namespace Bitrix\Main\Web;

use \DomainException;
use \InvalidArgumentException;
use \UnexpectedValueException;
use \DateTime;

/**
 * JSON Web Token implementation, based on this spec:
 * https://tools.ietf.org/html/rfc7519
 *
 * PHP version 5
 *
 * @category Authentication
 * @package  Authentication_JWT
 * @author   Neuman Vong <neuman@twilio.com>
 * @author   Anant Narayanan <anant@php.net>
 * @license  http://opensource.org/licenses/BSD-3-Clause 3-clause BSD
 * @link     https://github.com/firebase/php-jwt
 */
class JWT
{
	const ASN1_INTEGER = 0x02;
	const ASN1_SEQUENCE = 0x10;
	const ASN1_BIT_STRING = 0x03;

	/**
	 * When checking nbf, iat or expiration times,
	 * we want to provide some extra leeway time to
	 * account for clock skew.
	 */
	public static $leeway = 0;

	/**
	 * Allow the current timestamp to be specified.
	 * Useful for fixing a value within unit testing.
	 *
	 * Will default to PHP time() value if null.
	 */
	public static $timestamp = null;

	public static $supported_algs = array(
		'ES256' => array('openssl', 'SHA256'),
		'HS256' => array('hash_hmac', 'SHA256'),
		'HS384' => array('hash_hmac', 'SHA384'),
		'HS512' => array('hash_hmac', 'SHA512'),
		'RS256' => array('openssl', 'SHA256'),
		'RS384' => array('openssl', 'SHA384'),
		'RS512' => array('openssl', 'SHA512'),
	);

	/**
	 * Decodes a JWT string into a PHP object.
	 *
	 * @param string                    $jwt            The JWT
	 * @param string|array|resource     $key            The key, or map of keys.
	 *                                                  If the algorithm used is asymmetric, this is the public key
	 * @param array                     $allowed_algs   List of supported verification algorithms
	 *                                                  Supported algorithms are 'ES256', 'HS256', 'HS384', 'HS512', 'RS256', 'RS384', and 'RS512'
	 *
	 * @return object The JWT's payload as a PHP object
	 *
	 * @throws UnexpectedValueException     Provided JWT was invalid
	 *
	 * @uses jsonDecode
	 * @uses urlsafeB64Decode
	 */
	public static function decode($jwt, $key, array $allowed_algs = array())
	{
		$timestamp = is_null(static::$timestamp) ? time() : static::$timestamp;

		if (empty($key)) {
			throw new InvalidArgumentException('Key may not be empty');
		}
		$tks = explode('.', $jwt);
		if (count($tks) != 3) {
			throw new UnexpectedValueException('Wrong number of segments');
		}
		list($headb64, $bodyb64, $cryptob64) = $tks;
		if (null === ($header = static::jsonDecode(static::urlsafeB64Decode($headb64)))) {
			throw new UnexpectedValueException('Invalid header encoding');
		}
		if (null === $payload = static::jsonDecode(static::urlsafeB64Decode($bodyb64))) {
			throw new UnexpectedValueException('Invalid claims encoding');
		}
		if (false === ($sig = static::urlsafeB64Decode($cryptob64))) {
			throw new UnexpectedValueException('Invalid signature encoding');
		}
		if (empty($header->alg)) {
			throw new UnexpectedValueException('Empty algorithm');
		}
		if (empty(static::$supported_algs[$header->alg])) {
			throw new UnexpectedValueException('Algorithm not supported');
		}
		if (!in_array($header->alg, $allowed_algs)) {
			throw new UnexpectedValueException('Algorithm not allowed');
		}
		if ($header->alg === 'ES256') {
			// OpenSSL expects an ASN.1 DER sequence for ES256 signatures
			$sig = self::signatureToDER($sig);
		}

		if (is_array($key) || $key instanceof \ArrayAccess) {
			if (isset($header->kid)) {
				if (!isset($key[$header->kid])) {
					throw new UnexpectedValueException('"kid" invalid, unable to lookup correct key');
				}
				$key = $key[$header->kid];
			} else {
				throw new UnexpectedValueException('"kid" empty, unable to lookup correct key');
			}
		}

		// Check the signature
		if (!static::verify("$headb64.$bodyb64", $sig, $key, $header->alg)) {
			throw new UnexpectedValueException('Signature verification failed');
		}

		// Check the nbf if it is defined. This is the time that the
		// token can actually be used. If it's not yet that time, abort.
		if (isset($payload->nbf) && $payload->nbf > ($timestamp + static::$leeway)) {
			throw new UnexpectedValueException(
				'Cannot handle token prior to ' . date(DateTime::ISO8601, $payload->nbf)
			);
		}

		// Check that this token has been created before 'now'. This prevents
		// using tokens that have been created for later use (and haven't
		// correctly used the nbf claim).
		if (isset($payload->iat) && $payload->iat > ($timestamp + static::$leeway)) {
			throw new UnexpectedValueException(
				'Cannot handle token prior to ' . date(DateTime::ISO8601, $payload->iat)
			);
		}

		// Check if this token has expired.
		if (isset($payload->exp) && ($timestamp - static::$leeway) >= $payload->exp) {
			throw new UnexpectedValueException('Expired token');
		}

		return $payload;
	}

	/**
	 * Converts and signs a PHP object or array into a JWT string.
	 *
	 * @param object|array  $payload    PHP object or array
	 * @param string        $key        The secret key.
	 *                                  If the algorithm used is asymmetric, this is the private key
	 * @param string        $alg        The signing algorithm.
	 *                                  Supported algorithms are 'ES256', 'HS256', 'HS384', 'HS512', 'RS256', 'RS384', and 'RS512'
	 * @param mixed         $keyId
	 * @param array         $head       An array with header elements to attach
	 *
	 * @return string A signed JWT
	 *
	 * @uses jsonEncode
	 * @uses urlsafeB64Encode
	 */
	public static function encode($payload, $key, $alg = 'HS256', $keyId = null, $head = null)
	{
		$header = array('typ' => 'JWT', 'alg' => $alg);
		if ($keyId !== null) {
			$header['kid'] = $keyId;
		}
		if (isset($head) && is_array($head)) {
			$header = array_merge($head, $header);
		}
		$segments = array();
		$segments[] = static::urlsafeB64Encode(static::jsonEncode($header));
		$segments[] = static::urlsafeB64Encode(static::jsonEncode($payload));
		$signing_input = implode('.', $segments);

		$signature = static::sign($signing_input, $key, $alg);
		$segments[] = static::urlsafeB64Encode($signature);

		return implode('.', $segments);
	}

	/**
	 * Sign a string with a given key and algorithm.
	 *
	 * @param string            $msg    The message to sign
	 * @param string|resource   $key    The secret key
	 * @param string            $alg    The signing algorithm.
	 *                                  Supported algorithms are 'ES256', 'HS256', 'HS384', 'HS512', 'RS256', 'RS384', and 'RS512'
	 *
	 * @return string An encrypted message
	 *
	 * @throws DomainException Unsupported algorithm was specified
	 */
	public static function sign($msg, $key, $alg = 'HS256')
	{
		if (empty(static::$supported_algs[$alg])) {
			throw new DomainException('Algorithm not supported');
		}
		list($function, $algorithm) = static::$supported_algs[$alg];
		switch ($function) {
			case 'hash_hmac':
				return hash_hmac($algorithm, $msg, $key, true);
			case 'openssl':
				$signature = '';
				$success = openssl_sign($msg, $signature, $key, $algorithm);
				if (!$success) {
					throw new DomainException("OpenSSL unable to sign data");
				} else {
					if ($alg === 'ES256') {
						$signature = self::signatureFromDER($signature, 256);
					}
					return $signature;
				}
		}
	}

	/**
	 * Verify a signature with the message, key and method. Not all methods
	 * are symmetric, so we must have a separate verify and sign method.
	 *
	 * @param string            $msg        The original message (header and body)
	 * @param string            $signature  The original signature
	 * @param string|resource   $key        For HS*, a string key works. for RS*, must be a resource of an openssl public key
	 * @param string            $alg        The algorithm
	 *
	 * @return bool
	 *
	 * @throws DomainException Invalid Algorithm or OpenSSL failure
	 */
	private static function verify($msg, $signature, $key, $alg)
	{
		if (empty(static::$supported_algs[$alg])) {
			throw new DomainException('Algorithm not supported');
		}

		list($function, $algorithm) = static::$supported_algs[$alg];
		switch ($function) {
			case 'openssl':
				$success = openssl_verify($msg, $signature, $key, $algorithm);
				if ($success === 1) {
					return true;
				} elseif ($success === 0) {
					return false;
				}
				// returns 1 on success, 0 on failure, -1 on error.
				throw new DomainException(
					'OpenSSL error: ' . openssl_error_string()
				);
			case 'hash_hmac':
			default:
				$hash = hash_hmac($algorithm, $msg, $key, true);
				if (function_exists('hash_equals')) {
					return hash_equals($signature, $hash);
				}
				$len = min(static::safeStrlen($signature), static::safeStrlen($hash));

				$status = 0;
				for ($i = 0; $i < $len; $i++) {
					$status |= (ord($signature[$i]) ^ ord($hash[$i]));
				}
				$status |= (static::safeStrlen($signature) ^ static::safeStrlen($hash));

				return ($status === 0);
		}
	}

	/**
	 * Decode a JSON string into a PHP object.
	 *
	 * @param string $input JSON string
	 *
	 * @return object Object representation of JSON string
	 *
	 * @throws DomainException Provided string was invalid JSON
	 */
	public static function jsonDecode($input)
	{
		if (version_compare(PHP_VERSION, '5.4.0', '>=') && !(defined('JSON_C_VERSION') && PHP_INT_SIZE > 4)) {
			/** In PHP >=5.4.0, json_decode() accepts an options parameter, that allows you
			 * to specify that large ints (like Steam Transaction IDs) should be treated as
			 * strings, rather than the PHP default behaviour of converting them to floats.
			 */
			$obj = json_decode($input, false, 512, JSON_BIGINT_AS_STRING);
		} else {
			/** Not all servers will support that, however, so for older versions we must
			 * manually detect large ints in the JSON string and quote them (thus converting
			 *them to strings) before decoding, hence the preg_replace() call.
			 */
			$max_int_length = strlen((string) PHP_INT_MAX) - 1;
			$json_without_bigints = preg_replace('/:\s*(-?\d{'.$max_int_length.',})/', ': "$1"', $input);
			$obj = json_decode($json_without_bigints);
		}

		if ($errno = json_last_error()) {
			static::handleJsonError($errno);
		} elseif ($obj === null && $input !== 'null') {
			throw new DomainException('Null result with non-null input');
		}
		return $obj;
	}

	/**
	 * Encode a PHP object into a JSON string.
	 *
	 * @param object|array $input A PHP object or array
	 *
	 * @return string JSON representation of the PHP object or array
	 *
	 * @throws DomainException Provided object could not be encoded to valid JSON
	 */
	public static function jsonEncode($input)
	{
		$json = json_encode($input);
		if ($errno = json_last_error()) {
			static::handleJsonError($errno);
		} elseif ($json === 'null' && $input !== null) {
			throw new DomainException('Null result with non-null input');
		}
		return $json;
	}

	/**
	 * Decode a string with URL-safe Base64.
	 *
	 * @param string $input A Base64 encoded string
	 *
	 * @return string A decoded string
	 */
	public static function urlsafeB64Decode($input)
	{
		$remainder = strlen($input) % 4;
		if ($remainder) {
			$padlen = 4 - $remainder;
			$input .= str_repeat('=', $padlen);
		}
		return base64_decode(strtr($input, '-_', '+/'));
	}

	/**
	 * Encode a string with URL-safe Base64.
	 *
	 * @param string $input The string you want encoded
	 *
	 * @return string The base64 encode of what you passed in
	 */
	public static function urlsafeB64Encode($input)
	{
		return str_replace('=', '', strtr(base64_encode($input), '+/', '-_'));
	}

	/**
	 * Helper method to create a JSON error.
	 *
	 * @param int $errno An error number from json_last_error()
	 *
	 * @return void
	 */
	private static function handleJsonError($errno)
	{
		$messages = array(
			JSON_ERROR_DEPTH => 'Maximum stack depth exceeded',
			JSON_ERROR_STATE_MISMATCH => 'Invalid or malformed JSON',
			JSON_ERROR_CTRL_CHAR => 'Unexpected control character found',
			JSON_ERROR_SYNTAX => 'Syntax error, malformed JSON',
			JSON_ERROR_UTF8 => 'Malformed UTF-8 characters' //PHP >= 5.3.3
		);
		throw new DomainException(
			$messages[$errno] ?? 'Unknown JSON error: '.$errno
		);
	}

	/**
	 * Get the number of bytes in cryptographic strings.
	 *
	 * @param string $str
	 *
	 * @return int
	 */
	private static function safeStrlen($str)
	{
		if (function_exists('mb_strlen')) {
			return mb_strlen($str, '8bit');
		}
		return strlen($str);
	}

	/**
	 * Convert an ECDSA signature to an ASN.1 DER sequence
	 *
	 * @param   string $sig The ECDSA signature to convert
	 * @return  string The encoded DER object
	 */
	private static function signatureToDER($sig)
	{
		// Separate the signature into r-value and s-value
		list($r, $s) = str_split($sig, (int) (strlen($sig) / 2));

		// Trim leading zeros
		$r = ltrim($r, "\x00");
		$s = ltrim($s, "\x00");

		// Convert r-value and s-value from unsigned big-endian integers to
		// signed two's complement
		if (ord($r[0]) > 0x7f) {
			$r = "\x00" . $r;
		}
		if (ord($s[0]) > 0x7f) {
			$s = "\x00" . $s;
		}

		return self::encodeDER(
			self::ASN1_SEQUENCE,
			self::encodeDER(self::ASN1_INTEGER, $r) .
			self::encodeDER(self::ASN1_INTEGER, $s)
		);
	}

	/**
	 * Encodes a value into a DER object.
	 *
	 * @param   int     $type DER tag
	 * @param   string  $value the value to encode
	 * @return  string  the encoded object
	 */
	private static function encodeDER($type, $value)
	{
		$tag_header = 0;
		if ($type === self::ASN1_SEQUENCE) {
			$tag_header |= 0x20;
		}

		// Type
		$der = chr($tag_header | $type);

		// Length
		$der .= chr(strlen($value));

		return $der . $value;
	}

	/**
	 * Encodes signature from a DER object.
	 *
	 * @param   string  $der binary signature in DER format
	 * @param   int     $keySize the nubmer of bits in the key
	 * @return  string  the signature
	 */
	private static function signatureFromDER($der, $keySize)
	{
		// OpenSSL returns the ECDSA signatures as a binary ASN.1 DER SEQUENCE
		list($offset, $_) = self::readDER($der);
		list($offset, $r) = self::readDER($der, $offset);
		list($offset, $s) = self::readDER($der, $offset);

		// Convert r-value and s-value from signed two's compliment to unsigned
		// big-endian integers
		$r = ltrim($r, "\x00");
		$s = ltrim($s, "\x00");

		// Pad out r and s so that they are $keySize bits long
		$r = str_pad($r, $keySize / 8, "\x00", STR_PAD_LEFT);
		$s = str_pad($s, $keySize / 8, "\x00", STR_PAD_LEFT);

		return $r . $s;
	}

	/**
	 * Reads binary DER-encoded data and decodes into a single object
	 *
	 * @param string $der the binary data in DER format
	 * @param int $offset the offset of the data stream containing the object
	 * to decode
	 * @return array [$offset, $data] the new offset and the decoded object
	 */
	private static function readDER($der, $offset = 0)
	{
		$pos = $offset;
		$size = strlen($der);
		$constructed = (ord($der[$pos]) >> 5) & 0x01;
		$type = ord($der[$pos++]) & 0x1f;

		// Length
		$len = ord($der[$pos++]);
		if ($len & 0x80) {
			$n = $len & 0x1f;
			$len = 0;
			while ($n-- && $pos < $size) {
				$len = ($len << 8) | ord($der[$pos++]);
			}
		}

		// Value
		if ($type == self::ASN1_BIT_STRING) {
			$pos++; // Skip the first contents octet (padding indicator)
			$data = substr($der, $pos, $len - 1);
			$pos += $len - 1;
		} elseif (!$constructed) {
			$data = substr($der, $pos, $len);
			$pos += $len;
		} else {
			$data = null;
		}

		return array($pos, $data);
	}
}